Madras HC halts further works at Periyakulam, Valankulam in Coimbatore as expert report flags wetland bird decline

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A flock of Spot-Billed Pelicans at the Ukkadam Big Tank in Coimbatore. | Photo Credit: PERIASAMY M.

The Madras High Court (HC) has directed that further developmental activities, including ongoing and proposed projects, at Periyakulam (Ukkadam Big Tank) and Valankulam lakes in Coimbatore be halted until a Wetland Management Plan is implemented, after an expert report flagged a decline in wetland-dependent bird species in the two water bodies.

A special Division Bench of Justices N. Sathish Kumar and K. Rajasekar, in an order dated August 14, also directed the authorities to set right the Sewage Treatment Plants (STPs) at the two lakes and prevent untreated wastewater from flowing into them.

The directions followed a report submitted by the Salim Ali Centre for Ornithology and Natural History, Coimbatore, which was asked to study whether the lake revitalisation activities undertaken by the Coimbatore Municipal Corporation were detrimental to birds nesting and using the water bodies.

The Centre noted that eight ecologically and hydrologically interconnected lakes within the Corporation limits were associated with River Noyyal and that birds, particularly migratory species, moved between the lakes. For the present study, however, it examined Periyakulam and Valankulam lakes.

According to the report, 183 bird species had been recorded at Periyakulam, comprising 126 resident and 57 migratory species. Eight species were globally threatened, including two vulnerable species — the Curlew Sandpiper and River Tern — and six near-threatened species.

At Valankulam, 104 species had been recorded, including 86 resident and 18 migratory species. Four species were classified as threatened, including the vulnerable River Tern and three near-threatened species.

The expert report said the overall bird composition had shifted towards woodland species, with only a few generalist wetland birds remaining. It said the change indicated a transformation of the wetland ecosystem into an area “manicured for recreational use”.

At Periyakulam, several wetland-associated species had shown a moderate to major decline in reporting frequency since September 2018. Nearly 78% of high-priority waterbirds listed in the State of India Birds dataset had recorded a reduction in reporting frequency, the report said.

The report also noted declining trends among threatened species, including the River Tern, Black-tailed Godwit and Spot-billed Pelican. Several other wetland birds had not been recorded at the lake in recent years.

Similar concerns were reported at Valankulam, where several wetland-associated species showed declining reporting frequencies after the implementation of the lake development scheme.

The Centre also found that the STPs at both lakes were not functioning and untreated wastewater was flowing into the water bodies, making them unhealthy for aquatic life, including birds.

Taking note of the findings, the Bench directed the authorities to immediately set right the STPs and prevent untreated wastewater from entering the lakes.